As commonly known, aluminum production consumes a large amount of electrical energy. In a typical aluminum refinery, every cell can be controlled individually by the operator. The cell voltage is displayed on an analog voltmeter which has an operating range of 0-8 volts. There is a known cell voltage at which the cells should be maintained to ensure efficient cell operation. In practice, the operator reads the cell voltage from the analog meter and makes a manual adjustment if necessary. Considering the rapidly increasing cost of electrical energy, this system needs refinement. The following is a list of the main disadvantages of the present analog voltmeter system:
(1) Read-out accuracy of the present analog voltmeters is not better than .+-.100 millivolts.
(2) The electro-mechanical voltmeter movement is sensitive to shock and vibration.
(3) The voltmeter is using magnetic field to deflect the pointer; therefore auxiliary magnetic fields adversely affect the accuracy of such voltmeters.
(4) The small amount of hydrogen fluoride present in aluminum refineries attacks the front glass of the voltmeter and this further reduces the read-out accuracy.